Domestic appliance

ABSTRACT

A receptacle of a hand washing station includes a heat exchanger having an external surface for thermally contacting a relatively hot fluid and an internal surface for thermally contacting a relatively cold fluid. The external surface of the heat exchanger forms at least part of the external surface of the receptacle.

REFERENCE TO RELATED APPLICATIONS

This application claims the priority of United Kingdom Application No.1121298.2, filed on 12 Dec. 2011, the entire contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a hand washing station. In one example,the hand washing station is in the form of a sink unit which may beinstalled in a washroom.

BACKGROUND OF THE INVENTION

As is known, a sink unit comprises at least one fluid dispenser, usuallyin the form of a tap for dispensing water, for dispensing fluid into areceptacle, and a drain for draining the dispensed fluid from thereceptacle. The sink unit may be provided with a single tap fordispensing water over a range of different temperatures, or two tapseach of dispensing water of a respective temperature. The fluiddispenser may be located adjacent to the receptacle, mounted on thereceptacle, or located on a wall.

The amount of energy used per year to heat water supplied to a sink unitcan be significant. By way of example, a sink unit located in a publicwashroom with a medium footfall may be subject to around 200 uses perday. If each user of the sink unit chooses to wash with relatively hotwater, typically dispensed at around 40° C., and to use around 330 ml ofwater per wash (calculated from a dispensed flow rate of 2 liters perminute and a wash time of 10 seconds) then the energy required to heatthe water supplied to the sink unit over the course of the year from atemperature of around 18° C. to 40° C., may be around 625 kWh.

The temperature drop in the dispensed hot water as the dispensed waterpasses through the air and then over the hands of the user and on to theexternal surface of the receptacle to the drain is generally around 5°C. Consequently, the energy wasted as the hot water is expelled throughthe drain of the sink unit may be around 485 kWh per year.

It is known to provide a system for transferring heat from waste hotwater expelled from the drain of a receptacle to incoming cold water tobe supplied to the receptacle, and so reduce the amount of energyrequired to heat the incoming cold water before it is dispensed. Forexample, U.S. Pat. No. 4,291,423 describes a heat recovery system inwhich the waste hot water is conveyed from a receptacle to a channellocated beneath the receptacle and housing a tube containing theincoming cold water. Heat is transferred from the waste hot water to theincoming cold water through the body of the tube.

However, the build up of soap, scum and hard water scale on the outersurface of the tube can impair the transfer of heat to the incoming coldwater, and so the receptacle needs to be removable to enable a user toaccess the heat recovery system for cleaning. This can be inconvenientfor the user.

SUMMARY OF THE INVENTION

In a first aspect the present invention provides a hand washing stationor unit, for example a sink unit, comprising a receptacle having adrain, and a fluid dispenser for dispensing fluid into the receptacle,the receptacle comprising a heat exchanger for transferring heat betweenthe dispensed fluid and a second fluid, the heat exchanger forming atleast part of an external surface of the receptacle.

The heat exchanger thus forms part of the receptacle into which fluid isdispensed. The heat exchanger is arranged to transfer heat between thedispensed fluid and a second fluid, which may be at a lower temperaturethan the dispensed fluid within the receptacle. This allows the heatexchanger to extract heat from the dispensed fluid before the dispensedfluid enters the drain, and so following only a relatively small drop intemperature of the dispensed fluid, for example through contact with auser's hands and/or air. This can significantly improve the recovery ofheat from the dispensed fluid in comparison to a thermal recovery systemin which heat is transferred from the dispensed fluid following itsexhaust from the drain or admission into an enclosed channel, asdescribed in U.S. Pat. No. 4,291,423, and thus following a greater dropin its temperature. As used herein, the term “external surface of thereceptacle” includes any surface which is contacted by the dispensedfluid before the dispensed fluid enters the drain of the receptacle. Thereceptacle may be in the form of a bowl or basin into which fluid isdispensed.

The location of the heat exchanger so that it forms at least part of anexternal surface of the receptacle into which the fluid is dispensed canenable the external surface of the heat exchanger, which is in thermalcontact with the dispensed fluid, to be readily cleaned by a user.Through regular cleaning of the external surface of the receptacle,usually performed at least two or three times per day in a publicwashroom, the external surface of the heat exchanger can also be keptclean, thereby maintaining the efficiency of the heat exchanger.

This location of the heat exchanger places the external surface of theheat exchanger in contact with another fluid other than the dispensedfluid, such as the air in the ambient atmosphere. Depending on therelative temperatures of the ambient atmosphere and the second fluid,the heat exchanger can transfer heat from a relatively hot ambientatmosphere to a relatively cold second fluid when there is no dispensedfluid within the receptacle. For example, there are various heat sourceswithin a public washroom which may contribute to heating the air abovethe temperature of the second fluid, including users of the washroom,hot air hand driers, and radiators. Alternatively, when the ambientatmosphere is relatively cold the heat exchanger can transfer heat tothe relatively cold ambient atmosphere from the relatively hot secondfluid.

Therefore, in a second aspect the present invention provides a handwashing station comprising a receptacle, the receptacle comprising aheat exchanger having an external surface for thermally contacting afluid at a first temperature and an internal surface for thermallycontacting a fluid at a second temperature, the external surface of theheat exchanger forming at least part of the external surface of thereceptacle.

As discussed above, the fluid at the first temperature may be hotter, orcolder, than the fluid at the second temperature. The fluid at the firsttemperature may be a dispensed fluid, such as dispensed water ordispensed air, or air within the ambient atmosphere. For example, airmay be dispensed from a fan for circulating air with a washroom orlocally adjacent to the receptacle, or from a hand dryer. This fluid atthe first temperature is referred to hereafter as “the dispensed fluid”.The fluid at the second temperature is referred to hereafter as “thesecond fluid”, and this may be water received from a mains water supply,or air. For example, the air may be pumped to the hand washing stationfrom an external source, or from air located outside a washroom in whichthe hand washing station is installed. The second fluid may besubsequently utilised to form the dispensed fluid, and so the dispensedfluid and the second fluid may vary from one another solely throughtheir respective temperatures.

The external surface of the heat exchanger may have any desired shape.For example, the external surface of the heat exchanger may form agenerally flat or planar external surface of the receptacle whichcontacts the dispensed fluid and/or the ambient atmosphere. However, toincrease the area of the external surface of the heat exchanger, and soincrease the surface area available for heat transfer within a givenreceptacle space, the heat exchanger preferably forms at least part of araised external surface of the receptacle. Alternatively, oradditionally, the external surface of the heat exchanger may form aconcave external surface of the receptacle for guiding the dispensedfluid towards the drain.

To optimise the transfer of fluid to the second fluid, it is preferableto convey a flow of the second fluid over or adjacent to an internalsurface of the heat exchanger in a direction which is opposite to thedirection in which the dispensed fluid flows over the external surfaceof the heat exchanger. Providing at least part of the external surfaceof the heat exchanger with a raised shape, such as a domed or convexshape, can enable the sink unit to be arranged, for example throughselection of at least one of the relative positions of the dispenser andthe heat exchanger, the shape of the dispenser, and the rate at whichfluid is dispensed, so that the dispensed fluid will flow over theexternal surface of the heat exchanger in a common direction, that is,away from an apex of the raised surface. The second fluid may then beconveyed over or adjacent to the concave internal surface of the heatexchanger towards the apex.

A benefit of forming the heat exchanger with a convex external surfaceis that the dispensed fluid can tend to form a relatively thin film overthe convex surface, with a reduced surface area in comparison to that ofmany water droplets running over the convex surface. This can reduce thedegree of evaporative cooling of the dispensed fluid, and so maximisethe transfer of heat through the heat exchanger. The external surface ofthe heat exchanger is preferably formed from, or coated with, ahydrophilic material to promote the spreading of the dispensed fluidover the heat exchanger, and so promote the transfer of heat through the(relatively conductive) heat exchanger rather than to the (relativelyinsulating) ambient atmosphere.

The raised portion of the heat exchanger may have any desiredgeometrical shape. For example, the raised portion of the heat exchangermay have a domed, cylindrical, conical, frusto-conical or polyhedralshape. The heat exchanger preferably forms at least part of an externalsurface of the receptacle which has a substantially spherical curvatureso that the dispensed fluid spreads evenly over the heat exchanger toform a laminar film. As a hemisphere has twice the surface area of acircular flat disc of equal radius, shaping the heat exchanger in thismanner can maximise the volume of fluid in thermal contact with the heatexchanger per second, and so maximise the rate of heat transfer to thesecond fluid. With this shape, the heat exchanger may also be relativelyinsensitive to the installation angle of the heat exchanger relative tothe fluid dispenser.

A sphere is also one of the strongest and robust of three dimensionalshapes, and this can enable at least the section of the heat exchangerwhich forms this spherical section of the external surface of thereceptacle to be formed from material having a thickness of less than 5mm, preferably less than 2 mm and more preferably less than 1 mm. Thiscan reduce the time taken to heat the heat exchanger to the temperatureof the dispensed fluid, and can reduce the amount of heat that isretained by the heat exchanger between uses of the sink unit. Thethickness of the heat exchanger and hence its material volume isproportional the thermal inertia and the sensitivity of the heatexchanging system. A low inertia heat exchanging system can respondrapidly to small changes in temperature, allowing heat to be transferredbetween the ambient atmosphere and the second fluid.

The heat exchanger may thus form a flat, domed, convex, cylindrical,conical, frustoconical, polyhedral, hemispherical, spheroidal orspherical part of the receptacle. This part of the receptacle may beproud of at least part of an external surface of a base of thereceptacle. Dispensed fluid may then flow over this part of thereceptacle and on to the base before being exhausted through the drain.The receptacle may have a side wall connected to the base, and whichextends about the heat exchanger. Alternatively, the heat exchanger maybe located above the side wall of the receptacle.

The heat exchanger may be a separate component from the base of thereceptacle. For example, the heat exchanger may be connected to the baseof the receptacle so that the heat exchanger is located above the drainof the receptacle. The heat exchanger may be connected to the base ofthe receptacle by a plurality of supports extending about the peripheryof the heat exchanger so that dispensed fluid may run off the edge ofthe heat exchanger and subsequently pass beneath the heat exchanger tothe drain. The heat exchanger may be removably connected to thereceptacle to allow the heat exchanger to be cleaned, repaired orreplaced without having to remove any other part of the receptacle.

In a preferred embodiment, the heat exchanger is integral with thereceptacle. The heat exchanger preferably forms at least part of theexternal surface of the base of the receptacle. For the reasonsdiscussed above, the heat exchanger preferably forms at least part of araised section of the base. This raised section of the base ispreferably convex in shape, and preferably has a substantially sphericalcurvature. In a preferred embodiment, the heat exchanger forms ahemispherical section of the external surface of the base of thereceptacle. The sink unit is preferably arranged so that the fluid isdispensed directly on to the raised section of the base so that, whenthe flow of dispensed fluid does not impinge upon a user's hands, theexternal surface of the raised section of the receptacle can besubstantially evenly coated with the dispensed fluid as it flows towardsthe drain. For example, the fluid dispenser may be arranged such thatthe dispensed fluid is dispensed on to the apex of the raised section ofthe receptacle.

In a preferred embodiment, the receptacle comprises a side wall. As analternative from, or in addition to, the heat exchanger forming part ofthe base of the receptacle, the heat exchanger may form at least part ofthe external surface of the side wall of the receptacle. This can enableheat to be extracted from dispensed fluid which has splashed from auser's hands on to the external surface of the side wall of thereceptacle, and can also enable heat to be extracted between the ambientatmosphere and the second fluid. The side wall preferably extends aboutthe raised section of the base, and the drain is preferably locatedbetween the side wall and the raised section of the base. The drain maycomprise either a single fluid port, or a plurality of fluid portsspaced about the raised section of the base, through which fluid drainsfrom the receptacle to an external waste pipe.

The heat exchanger may comprise a single sheet of material which isshaped to form at least part of the external surface of the receptacle.The drain may be formed from punching or otherwise removing materialfrom this sheet of material. The sheet of material is preferably formedfrom metallic material, for example a stainless steel, so that the heatexchanger has a relatively high thermal conductivity. A coating ofhydrophilic material may be deposited or otherwise disposed on thissheet of material to form the external surface of the heat exchanger.Alternatively, the heat exchanger may comprise a plurality of layers ofmaterial, with one layer of material forming the external surface of theheat exchanger and another layer of material forming the internalsurface of the heat exchanger. In this case, the layers of the heatexchanger may be formed from the same material or from differentmaterials. For example, an external surface of the heat exchanger may beformed from a sheet of stainless steel whereas an internal surface ofthe heat exchanger may be formed from a sheet of a different metallicmaterial to reduce manufacturing costs, or from a sheet of plasticsmaterial to further separate the different fluid streams for reasons ofwater safety.

The receptacle preferably comprises means for conveying a flow of thesecond fluid adjacent to or over an internal surface of the heatexchanger, so that the second fluid is placed in thermal contact withthe heat exchanger to exchange heat with fluid within the receptacle.The fluid conveying means is preferably arranged to convey the secondfluid over or adjacent to the internal surface of the heat exchanger ina direction substantially opposite to that in which the dispensed fluidflows over the external surface of the heat exchanger. For example,where the heat exchanger comprises a convex section defining a convexexternal surface over which the dispensed fluid flows, the fluidconveying means is preferably arranged to convey the second fluidinternally towards an apex of the convex section of the heat exchanger.

The fluid conveying means may comprise at least one conduit forconveying fluid adjacent the internal surface of the heat exchanger. Forexample, the fluid conveying means may comprise one or more pipes ortubes which are arranged adjacent to the internal surface of the heatexchanger to place the second fluid in thermal contact with the internalsurface of the heat exchanger. For example, the pipe(s) may be woundabout a body or a casing over which the receptacle is located so thatthe pipe(s) are located internally opposite to the external surface ofthe heat exchanger.

In this case, the heat transferred between the dispensed fluid and thesecond fluid must also pass though the pipe(s), and so some of this heatmay be utilised to raise the temperature of the pipe(s) as opposed toraising the temperature of a relatively cold fluid. In view of this, ina preferred embodiment the receptacle comprises an enclosed fluidpassage in the form of a cooling jacket delimited at least in part bythe internal surface of the heat exchanger so that no additional thermalmass needs to be heated to conduct heat from relatively hot fluid torelatively cold fluid. The cooling jacket may extend over substantiallythe entire internal surface of the heat exchanger, and thus may extendover both the internal surface of the base of the receptacle and theinternal surface of the side walls of the receptacle. Alternatively, thecooling jacket may extend over selected sections of the internal surfaceof the receptacle.

The receptacle preferably comprises a casing extending about the heatexchanger, and the cooling jacket is preferably located between, andmore preferably delimited by, the heat exchanger and the casing. Theinternal surface of the heat exchanger and the internal surface of thecasing preferably have substantially the same shape so that the coolingjacket has a uniform thickness about the heat exchanger. The casing maybe arranged to transfer heat between fluid within the cooling jacket andthe ambient atmosphere in thermal contact with the external surface ofthe casing. An air dispenser, such as a fan, may be provided fordispensing air over the external surface of the casing so that heat canbe transferred between the dispensed air and the fluid within thecooling jacket. In this case, the casing may also form a heat exchangerof the receptacle. For example, the casing may be formed from metallicmaterial, such as a stainless steel. Alternatively, the casing may beformed from a thermally insulating material to inhibit loss of heatthrough the casing.

The casing preferably has a side wall comprising at least one fluidinlet port through which the second fluid enters the cooling jacket. Thecooling jacket may then convey fluid over the internal surface of theside wall of the heat exchanger. The cooling jacket may comprise aplurality of fluid inlet ports arranged about the side wall of thecasing for distributing evenly the second fluid over the internalsurface of the heat exchanger. An annular distribution jacket may beprovided for supplying fluid to the fluid inlet ports. Where the base ofthe heat exchanger comprises a raised section having a convex externalsurface, a fluid outlet port of the cooling jacket is preferably locatedopposite to the apex of the convex external surface.

The sink unit preferably comprises an inlet conduit for supplying fluidto the cooling jacket. The inlet conduit may be connected to a mainswater supply, which may have a high water pressure, for example up to 10bar. As an increase in the thickness of the heat exchanger—to allow thereceptacle to withstand a high pressure cold water supply to the coolingjacket—may be detrimental to the transfer of heat through the heatexchanger, the inlet conduit may comprise a pressure reducing valve forreducing the static pressure of the second fluid before it enters thecooling jacket. This can also inhibit any leakage of fluid from thecooling jacket through reducing the likelihood of any leaks formingwithin any seals or connections between the heat exchanger and thecasing due to the pressure of the fluid within the cooling jacket. Theinlet conduit may comprise a solenoid valve or other valve forselectively inhibiting the flow of fluid to the cooling jacket.

The sink unit may comprise an outlet conduit for conveying fluid fromthe cooling jacket to the fluid dispenser. A second valve, preferably asolenoid valve, may be provided between the cooling jacket and the fluiddispenser for inhibiting the dispensing of fluid from the fluiddispenser. This second valve may be located in the outlet conduit, or inanother conduit located between the outlet conduit and the fluiddispenser. The second conduit may be selectively opened, either manuallyby the user or in response to the detection of the user's hand proximateto the fluid dispenser, to cause fluid to be dispensed. When fluid is tobe dispensed from the fluid dispenser, the valves located in the inletconduit and the outlet conduit are preferably opened simultaneously.When the dispensing of fluid from the fluid dispenser is to be stopped,for example after a predetermined time or after a predetermined amountof fluid has been dispensed, the valve located in the inlet conduit ispreferably closed before the valve located in the outlet conduit. Thisprevents an undesirably high static pressure from being generated withinthe cooling jacket.

A heater may be provided for heating fluid located within the outletconduit to form the fluid which is dispensed from the fluid dispenser.Through the heat exchanger raising the temperature of the fluid as itpasses through the receptacle, less power is required to further heatthe fluid to the required dispensing temperature. At least part of theheater may be surrounded by the raised section of the base to reduce thelength of any exposed section of the outlet conduit located between thejacket and the heater.

Alternatively, the outlet conduit may convey fluid from the coolingjacket to a thermostatic mixing valve having a first inlet for receivingfluid from the outlet conduit, a second inlet for receiving a relativelyhot fluid, and an outlet connected to the fluid dispenser. Therelatively hot fluid may be a boiler-heated fluid which is mixed withthe fluid received from the cooling jacket to provide a mixed fluidwhich is supplied to the fluid dispenser to form the dispensed fluid. Inthis case, less boiler-heated fluid is required to provide a mixed fluidat the required dispensing temperature, thereby reducing the amount ofenergy consumed by the boiler. Again, at least part of the thermostaticmixing valve may be surrounded by the raised section of the base toreduce the length of any exposed section of the outlet conduit locatedbetween the jacket and the thermostatic mixing valve. In this case, avalve for inhibiting the dispensing of fluid from the fluid dispensermay be located between the thermostatic mixing valve and the fluiddispenser.

As an alternative to conveying fluid from the cooling jacket of areceptacle to the fluid dispenser for dispensing fluid into thatreceptacle, the fluid from the cooling jacket may be conveyed to a fluiddispenser of an adjacent sink unit. As another alternative, the sinkunit may form part of a series of sink units connected to a common mainswater supply for supplying cold water to the cooling jackets of thereceptacles of the sink units. The water exhausted from the coolingjackets may then be conveyed to a common thermostatic mixing valve formixing the water received from the receptacles of the sink units withhot water received from the boiler or other heater to provide a mixedfluid which is then supplied to the fluid dispensers of the sink unitsto form the dispensed fluid.

In a third aspect the present invention provides a hand washing station,for example a sink unit, comprising a receptacle with a raised sectionhaving a convex external surface, a fluid dispenser for dispensing arelatively hot fluid on to the convex external surface, and means forconveying a relatively cold fluid adjacent or over an internal surfaceof the raised section of the receptacle.

In a fourth aspect the present invention provides a hand washingstation, for example a sink unit, comprising a receptacle having a baseand a side wall connected to the base, and means for conveying arelatively cold fluid adjacent or over an internal surface of the sidewall of the receptacle.

In a fifth aspect the present invention provides a hand washing station,for example a sink unit, comprising a receptacle, a fluid dispenser fordispensing a relatively hot fluid into the receptacle, and a heatexchanger for transferring heat from relatively hot fluid within thereceptacle to a relatively cold fluid.

In a sixth aspect, the present invention provides a hand washingstation, for example a sink unit, comprising a fluid dispenser, areceptacle having a drain, a heat exchanger located above the drain andon to which the fluid dispenser is arranged to dispense fluid, and meansfor conveying a second fluid adjacent or over an internal surface of theheat exchanger. The heat exchanger is preferably connected to a base ofthe receptacle. The heat exchanger may form a side wall of thereceptacle, and/or at least part of a base of the receptacle.

Features described above in connection with the first aspect of theinvention are equally applicable to each of the second to sixth aspectsof the invention, and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features of the invention will now be described, by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view, from above, of a sink unit;

FIG. 2 is a top view of the sink unit;

FIG. 3 is a side sectional view taken along line J-J in FIG. 2,illustrating a system for conveying fluid from the receptacle of thesink unit to the fluid dispenser of the sink unit;

FIG. 4( a) is a detailed sectional view of a first example of the heatexchanger of the sink unit, and FIG. 4( b) is a detailed sectional viewof a second example of the heat exchanger of the sink unit;

FIG. 5 is another side sectional view taken along line J-J in FIG. 2,illustrating an alternative system for conveying fluid from thereceptacle of the sink unit to the fluid dispenser of the sink unit;

FIG. 6 is a similar view to FIG. 3, illustrating an air dispenser fordispensing air adjacent to the receptacle of the sink unit; and

FIG. 7 is a schematic illustration of the fluid paths in a washroomcomprising a plurality of sink units.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 to 3, an example of a hand washing stationcomprises a fluid dispenser and a receptacle for receiving the dispensedfluid. In this example, the hand washing station is in the form of asink unit 10, which comprises a receptacle in the form of a bowl orbasin 12 and a fluid dispenser 14 for dispensing fluid into the basin12. In this example, the basin 12 and the fluid dispenser 14 are eachinstalled on a counter 16. The fluid dispenser 14 is located adjacent tothe basin 12, but depending on the design of the sink unit 10 the fluiddispenser 14 may be connected directly to the basin 12 or on to a walllocated adjacent to the basin 12. The counter 16 has a first aperture 18into which the basin 12 is inserted so that a rim 20 of the basin 12 issupported by the upper surface of the counter 16. Alternatively, thebasin 12 may be connected to the lower surface of the counter 16 so asto be located directly beneath the first aperture 18. The counter 16 hasa second aperture 22 through which fluid is conveyed to the fluiddispenser 14 by a dispenser supply pipe 24 connected to the fluiddispenser 14.

In this example, the fluid dispenser 14 is in the form of a tap fordispensing hot water into the basin 12. The fluid dispenser 14 comprisesa main body 26 for receiving a flow of hot water from the dispensersupply pipe 24, and a spout 28 from which the hot water is dispensedinto the basin 12. On demand, hot water for washing is supplied from thesupply pipe 24 to the main body 26. The hot water runs inside the mainbody 26 and the spout 28 to an outlet 30 provided at the end of thespout 28. The fluid dispenser 14 is configured for “hands-free”operation using a conventional sensor and control loop whichautomatically opens a first stop valve 31 in the dispenser supply pipe24 in response to detection of a user's hands in a washing position.Alternatively, the fluid dispenser 14 may be configured for manualoperation.

In this example, the basin 12 has a generally circular outer periphery,but the basin 12 may have a rectangular or square periphery so as todefine a volume of any desired size or shape for receiving the dispensedhot water. This volume is delimited by the external surface of a base32, and the external surface of a side wall 34. The basin 12 comprises adrain 36 for exhausting dispensed hot water to a waste water pipe 38.

The base 32 has a central raised section 40. In this example, the raisedsection 40 has a convex external surface, which is preferablysubstantially hemispherical in shape. The apex 42 of the raised section40 of the base 32 may be approximately level with the rim 20 of thebasin 12 so that the side wall 34 surrounds the raised section 40 of thebase 32. The outlet 30 of the spout 28 of the fluid dispenser 14 isarranged to convey a flow of hot water on to the raised section 40 ofthe base 32. In this example, the outlet 30 of the spout 28 of the fluiddispenser 14 is located immediately above the apex 42 of the domedsection 40 of the base 32 so that, in the absence of a user's handsbeneath the spout 28, hot water is dispensed directly on to the apex 42of the domed section 40 of the base 32. However, the fluid dispenser 14may be arranged to direct the hot water on to a different part of thedomed section 40 of the base 32. The drain 36 comprises a plurality ofwaste outlet ports formed in the base 32, and spaced about the raisedsection 40 of the base 32.

The basin 12 comprises a heat exchanger 44 for transferring heat fromhot dispensed water within the basin 12 to a relatively cold fluid, inthis example cold water. The heat exchanger 44 forms the externalsurface of the base 32 and the side wall 34 of the basin 12. In thisexample, the heat exchanger 44 comprises a sheet of metallic material,preferably a stainless steel. Material is removed from the sheet, forexample by stamping or cutting, to form the fluid ports in the base 32for conveying waste hot water to the waste water pipe 38. With referenceto FIG. 4( a), the heat exchanger 44 may comprises a plurality of layersof sheet material. For example, an outer sheet 45 a of stainless steelmay provide the external surface 44 a of the heat exchanger 44, whereasan inner sheet 45 b of a different material, for example a plasticsmaterial, may provide the internal surface 44 b of the heat exchanger44. Alternatively, as illustrated in FIG. 4( b), the heat exchanger 44may comprise a single sheet of material, for example a stainless steel,providing both the external surface 44 a and the internal surface 44 bof the heat exchanger 44.

The basin 12 includes a fluid passage for conveying cold water from amains water supply over the internal surface 44 b of the heat exchanger44. In this example the fluid passage is located within the basin 12,and is in the form of a cooling jacket 46 which surrounds the internalsurface 44 b of the heat exchanger 44. With reference also to FIGS. 4(a) and 4(b), the cooling jacket 46 is delimited by the internal surface44 b of the heat exchanger 44 and the internal surface 48 b of a casing48 within which the heat exchanger 44 is located. The internal surface48 b of the casing 48 has substantially the same shape as the internalsurface 44 b of the heat exchanger 44 so that the cooling jacket 46 hasa substantially constant thickness about the heat exchanger 44. Thecasing 48 may be formed from a material having a similar thermalconductivity as the heat exchanger 44, and so may also be formed fromstainless steel. However, the casing 48 may be formed from, or have anexternal surface coated with, a thermally insulating material to inhibitthe loss of heat from the external surface 48 a of the casing 48. Thecasing 48 may be bonded, welded or otherwise joined at the base 32and/or the side wall 34 to the heat exchanger 44 for strength, and tomaintain a constant thickness of the cooling jacket 46.

The casing 48 defines a lower surface of the rim 20 of the basin 12. Theheat exchanger 44 and the casing 48 are preferably connected together atthe rim 20 of the basin 12, for example by welding or another suitablejoining technique depending on the materials from which the heatexchanger 44 and the casing 48 are formed. The base 50 of the casing 48is formed with a plurality of waste outlet ports which are aligned withthe waste outlet ports of the base 32 of the heat exchanger 44 duringassembly of the basin 12. Annular inserts 52 are inserted into thealigned waste outlet ports to isolate the drain 36 from the coolingjacket 46.

The cooling jacket 46 comprises a plurality of fluid inlet ports 54formed at the upper end of a side wall 56 of the casing 48 fordistributing cold water evenly about the internal surface 44 b of theheat exchanger 44. The fluid inlet ports 54 are supplied with cold waterby an annular distribution jacket 58 formed in the casing 48 andextending about the cooling jacket 46. The distribution jacket 58 may bethermally insulated from the cooling jacket 46. The distribution jacket58 has an inlet 60 located towards the lower end thereof which isconnected to a cold water supply pipe 62. The cold water supply pipe 62may be connected to a mains water supply, in which case the cold watersupply pipe 62 may comprise a pressure reducing valve for reducing thestatic pressure of the cold water before it enters the distributionjacket 58. For example, the pressure reducing valve may be arranged toreduce the static pressure of the cold water to around 0.5 bar toinhibit the generation of leaks in a seal or connection between the heatexchanger 44 and the casing 48. The cold water supply pipe 62 may alsohouse a second stop valve 63 for selectively inhibiting the flow of coldwater to the distribution jacket 58. The cooling jacket 46 comprises afluid outlet port 64 located in a raised section 66 of the base 50 ofthe casing 48. The fluid outlet port 64 is located opposite to the apex42 of the raised section 40 of the base 32 of the heat exchanger 44.

The sink unit 10 includes a system for conveying cold water from thebasin 12 to the fluid dispenser 14. In this example, the fluid outletport 64 of the cooling jacket 46 is connected to an outlet pipe 68 forconveying water from the cooling jacket 46 to a first inlet 70 of athermostatic mixing valve 72. The mixing valve 72 has a second inlet 74connected to a hot water supply pipe 76, and an outlet 78 connected tothe dispenser supply pipe 24. The hot water supply pipe 76 may beconnected to a boiler or other source of hot water. As illustrated, thethermostatic mixing valve 72 is located externally of the basin 12, butthe thermostatic mixing valve 72 may be located beneath the casing 48 sothat it is at least partially surrounded by the raised section 66 of thebase 50 of the casing 48. This can provide the sink unit 10 with a morecompact configuration.

When the inlet 60 of the distribution jacket 58 is first connected tothe cold water supply pipe 62, the second stop valve 63 is opened sothat the distribution jacket 58 becomes filled with cold water. A bleedvalve may be located in the rim 20 of the basin 12 to expel airdisplaced as the distribution jacket 58 fills with water. The cold waterenters the cooling jacket 46 through the fluid inlet ports 54 and flowsthrough the cooling jacket 46 to the fluid outlet port 64. The coldwater flows through the outlet pipe 68 to the thermostatic mixing valve72, where the cold water mixes with hot water received from the hotwater supply pipe 76. Warm water exhausted from the thermostatic mixingvalve 72 enters the dispenser supply pipe 24 connected to the fluiddispenser 14. With the first stop valve 31 in a closed position, nowater is dispensed from the spout 28. Any air displaced from the coolingjacket 46 and outlet pipe 68 as these conduits fill with cold water isexpelled from the spout 28 when the fluid dispenser 14 is firstoperated. Once the cooling jacket 46, the distribution jacket 58 and theoutlet conduit 68 have filled with water, the second stop valve 63 isclosed.

The basin 12 is thus normally in a state in which the cooling jacket 46is filled with cold water. Heat may then be transferred between thewater within the cooling jacket 46 and the air in the ambientatmosphere. For example, in the event that the temperature of theambient atmosphere is greater than that of the water within the coolingjacket 46, heat will be transferred through the heat exchanger 44 to thewater within the cooling jacket 46. Depending on the material from whichthe casing 48 is formed, heat may also be transferred from the ambientatmosphere through the casing 48 to the water within the cooling jacket46. On the other hand, in the event that the temperature of the ambientatmosphere is lower than that of the water within the cooling jacket 46,heat will be transferred through the heat exchanger 44 from the waterwithin the cooling jacket 46 to the ambient atmosphere. Again, dependingon the material from which the casing 48 is formed, heat may also betransferred to the ambient atmosphere through the casing 48.

When a user actuates the second stop valve 63, warm water is dispensedfrom the fluid dispenser 14. The first stop valve 31 is openedsimultaneously with the second stop valve 63, for example by acontroller for actuating, or detecting actuation of, the second stopvalve 63. As warm water is dispensed from the fluid dispenser 14, thewater within the sink unit 10 is replenished. Cold water is drawnthrough the cold water supply pipe 62, the dispensing jacket 58, thecooling jacket 46 and the outlet pipe 68, and hot water is drawn throughthe hot water supply pipe 76. When the user's hands are not locatedbeneath the spout 28, for example immediately following actuation of thefirst stop valve 31, the dispensed warm water impinges upon the apex 42of the raised section 40 of the base 32. The dispensed warm water runsdown the external surface 44 a of the raised section 40 and into thegully located between the side wall 34 and the raised section 40. Theshape of the raised section 40 causes the dispensed warm water todisperse evenly about the raised section 40 and pass in a generallylaminar flow towards the gully. Within the gully, the dispensed warmwater runs towards the drain 36, from where it is exhausted into thewaste water pipe 38.

As the dispensed warm water runs over the raised section 40 of the base32, heat is transferred through the heat exchanger 44 from the dispensedwarm water to the cold water flowing within the cooling jacket 46towards the fluid outlet port 64 located opposite to the apex 42. Heatis also transferred through the heat exchanger 44 to the cold waterwithin the cooling jacket 46 from the dispensed warm water runningwithin the gully to the drain 36.

When the user's hands are located beneath the spout 28, most of thedispensed water continues to fall from the user's hands on to the raisedsection 40 of the base 32. The introduction of soap into the dispensedwater from the user's hands can assist with the spreading of thedispensed water over the raised section 40 of the base 32, through thereduced surface tension of the soapy water. Some of the dispensed warmwater may splash from the user's hands on to the side wall 34. This warmwater runs over the external surface 44 a of the heat exchanger 44 andinto the gully. As the warm water runs over the external surface 44 a ofthe heat exchanger 44, heat is transferred from this warm water to thecold water flowing within the cooling jacket 46 over the internalsurface 44 b of the heat exchanger 44. Once an amount of warm water hasbeen dispensed from the fluid dispenser 14, the second stop valve 63 isclosed before the first stop valve 31 is closed to prevent anundesirably high static pressure from being generated within the coolingjacket 46.

The transfer of heat from the dispensed warm water located within thebasin 12, and also from the ambient atmosphere surrounding the basin 12,to the cold water within the cooling jacket 46 raises the temperature ofthe cold water before it is supplied to the thermostatic mixing valve72. For example, if water at a temperature of 40° C. is dispensed fromthe spout 28 at a flow rate of 2 liters per minute for 10 seconds, thetransfer of heat through a 0.7 mm thick stainless steel heat exchanger44 can raise the temperature of the cold water within the cooling jacket46 from a temperature of around 18° C. at the fluid inlet ports 54 to atemperature of around 28° C. at the fluid outlet port 64. This increasein the temperature of the cold water conveyed to the thermostatic mixingvalve 72 can significantly reduce the amount of hot water that needs tobe mixed with the cold water to produce warm water of a requireddispensing temperature, in this example of around 40° C. at the spout28. A reduction in the amount of hot water required to produce thedispensed warm water can provide energy savings through reducing theenergy expenditure of the boiler or other means for heating water toproduce the hot water.

FIG. 5 illustrates an alternative system for supplying water from thebasin 12 to the fluid dispenser 14. This system varies from thatillustrated in FIG. 3 insofar as the dispenser supply pipe 24 isconnected to the fluid outlet port 64 of the cooling jacket 46 via anelectric heater 80 for heating fluid exhausted from the cooling jacket46. At least part of the heater 80 is surrounded by the raised section40 of the base 32 so as to reduce the length of any piping between thefluid outlet port 64 and the heater 80. The sink unit 10 includes acontroller 82 connected by a first control line 84 to a thermocouple 86for detecting the temperature of the water exhausted from the coolingjacket 46. The controller 82 is connected to the heater 80 by a secondcontrol line 88 for actuating the heater 80 to raise the temperature ofthe water exhausted from the cooling jacket 46 to a desired dispensingtemperature, for example 40° C. at the spout 28. As the temperature atwhich water is exhausted from the cooling jacket 46 will vary, forexample, depending on variables such as the ambient temperature, and thefrequency of use of the fluid dispenser 14, the controller 82 may varythe power supplied to the heater 80 depending on the detectedtemperature so that warm water is dispensed from the fluid dispenser 14at the desired temperature.

In this example, the advantage provided by heating cold water within thecooling jacket 46 from a temperature of around 18° C. at the fluid inletports 54 to a temperature of around 28° C. at the fluid outlet port 64is that less energy is required at the heater 80 to heat the cold waterexhausted from the fluid outlet port 64 to the desired dispensingtemperature. For example, whereas around 3,000 W of energy may berequired to heat water from 18° C. to be dispensed from the spout 28 ata temperature of 40° C. at a flow rate of 2 liters per minute, onlyaround 1,680 W of energy may be required to heat the same flow rate ofwater from a temperature of 28° C. for dispensing from the spout 28 at40° C.

FIG. 6 illustrates a modification of the arrangement illustrated in FIG.3, and in which at least one air dispenser 88 is located adjacent to thebasin 12 for circulating an air flow within the ambient atmosphere ofthe sink unit 10. The arrangement illustrated in FIG. 5 may be similarlymodified. In this example, the sink unit 10 includes a first fan 88located above the counter 16. The first fan 88 may be located on thefluid dispenser 14, or it may be located elsewhere, for example adjacentthe fluid dispenser 14. Depending on the relative temperatures of thewater within the cooling jacket 46 and the ambient atmosphere, heat maybe conveyed through the heat exchanger 44 either to the water within thecooling jacket 46 or to the air in the ambient atmosphere. Asillustrated in FIG. 6, when the casing 48 is formed from a thermallyconductive material, a second fan 89 may be located beneath the counter16 so as to convey air over or adjacent the external surface 48 a of thecasing 48, which then acts as a heat exchanger for transferring heatbetween the air in thermal contact with the external surface of thecasing 48 and the water within the cooling jacket 46. Of course, thesecond fan 89 may be provided as an alternative to the first fan 88.

The sink unit 10 may be installed within a public washroom including aseries of sink units. Each of the sink units 10 may be configured asillustrated in FIG. 4, so that each sink unit 10 has a respective heater80, or as illustrated in FIG. 3 or FIG. 6, so that each sink unit 10includes a respective thermostatic mixing valve 72 for mixing cold waterreceived from the cooling jacket 46 with hot water supplied from arespective hot water supply pipe 76. Alternatively, each thermostaticmixing valve 72 may be connected to a common hot water supply pipe 76.

As an another alternative, as illustrated schematically in FIG. 7 theoutlet pipe 68 of each sink unit 10 may be connected to an inlet conduit92 for conveying water from each sink unit 10 to a common thermostaticmixing valve 72 connected to the hot water supply pipe 76. A pressurereducing valve 94 may be provided in the hot water supply pipe 76 forreducing the static pressure of the hot water to around 1 bar before itenters the thermostatic mixing valve 72. An outlet conduit 96 receives amixed fluid from the thermostatic mixing valve 72 and conveys the mixedfluid to the dispenser supply pipe 24 of each sink unit 10. The coldwater supply pipe 62 of each sink unit 10 is connected to a common mainswater supply pipe 98. The mains water supply pipe 98 may also include apressure reducing valve 100 for reducing the static pressure of the coldwater to around 1 bar before it enters the cold water supply pipes 62 ofthe sink units 10.

The invention claimed is:
 1. A hand washing station comprising areceptacle having a drain, the receptacle comprising a heat exchangerhaving an external surface for thermally contacting a fluid at a firsttemperature and an internal surface for thermally contacting a fluid ata second temperature, the external surface of the heat exchanger formingat least part of the external surface of the receptacle, the receptaclecomprising a fluid conveying system arranged to convey a flow of fluidadjacent to the internal surface of the heat exchanger, wherein thefluid conveying system is arranged to convey the flow of fluidinternally towards an apex of a convex section of the heat exchanger. 2.The hand washing station as claimed in claim 1, wherein the externalsurface of the heat exchanger forms at least part of a convex externalsurface of the receptacle.
 3. The hand washing station as claimed inclaim 1, wherein the external surface of the heat exchanger forms atleast part of an external surface of the receptacle which has asubstantially spherical curvature.
 4. The hand washing station asclaimed in claim 1, wherein the heat exchanger forms at least part of anexternal side wall of the receptacle.
 5. The hand washing station asclaimed in claim 1, wherein the heat exchanger forms at least part of anexternal base of the receptacle.
 6. The hand washing station as claimedin claim 5, wherein the heat exchanger forms part of a raised section ofthe base.
 7. The hand washing station as claimed in claim 6, wherein theraised section of the base is convex in shape.
 8. The hand washingstation as claimed in claim 6 or claim 7, wherein the raised section hasa substantially spherical curvature.
 9. The hand washing station asclaimed in claim 1, wherein the fluid conveying system is disposedinternally opposite said at least part of the external surface of thereceptacle.
 10. The hand washing station as claimed in claim 1, whereinthe fluid conveying system comprises a jacket delimited at least in partby the internal surface of the heat exchanger.
 11. The hand washingstation as claimed in claim 10, wherein the jacket comprises at leastone fluid inlet port.
 12. The hand washing station as claimed in claim10, wherein the jacket comprises a fluid outlet port.
 13. The handwashing station as claimed in claim 12, wherein the jacket has a domedsection, and the fluid outlet port is located at an apex of the domedsection of the jacket.
 14. The hand washing station as claimed in claim1, comprising an outlet conduit for receiving fluid from the fluidconveying system.
 15. The hand washing station as claimed in claim 14,comprising a heater for heating fluid located within the outlet conduit.